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-rw-r--r--compiler/rustc_abi/Cargo.toml24
-rw-r--r--compiler/rustc_abi/src/layout.rs945
-rw-r--r--compiler/rustc_abi/src/lib.rs1502
3 files changed, 2471 insertions, 0 deletions
diff --git a/compiler/rustc_abi/Cargo.toml b/compiler/rustc_abi/Cargo.toml
new file mode 100644
index 000000000..48b199cb8
--- /dev/null
+++ b/compiler/rustc_abi/Cargo.toml
@@ -0,0 +1,24 @@
+[package]
+name = "rustc_abi"
+version = "0.0.0"
+edition = "2021"
+
+[dependencies]
+bitflags = "1.2.1"
+tracing = "0.1"
+rand = { version = "0.8.4", default-features = false, optional = true }
+rand_xoshiro = { version = "0.6.0", optional = true }
+rustc_data_structures = { path = "../rustc_data_structures", optional = true }
+rustc_index = { path = "../rustc_index", default-features = false }
+rustc_macros = { path = "../rustc_macros", optional = true }
+rustc_serialize = { path = "../rustc_serialize", optional = true }
+
+[features]
+default = ["nightly", "randomize"]
+randomize = ["rand", "rand_xoshiro"]
+nightly = [
+ "rustc_data_structures",
+ "rustc_index/nightly",
+ "rustc_macros",
+ "rustc_serialize",
+]
diff --git a/compiler/rustc_abi/src/layout.rs b/compiler/rustc_abi/src/layout.rs
new file mode 100644
index 000000000..9c2cf58ef
--- /dev/null
+++ b/compiler/rustc_abi/src/layout.rs
@@ -0,0 +1,945 @@
+use super::*;
+use std::{
+ borrow::Borrow,
+ cmp,
+ fmt::Debug,
+ iter,
+ ops::{Bound, Deref},
+};
+
+#[cfg(feature = "randomize")]
+use rand::{seq::SliceRandom, SeedableRng};
+#[cfg(feature = "randomize")]
+use rand_xoshiro::Xoshiro128StarStar;
+
+use tracing::debug;
+
+// Invert a bijective mapping, i.e. `invert(map)[y] = x` if `map[x] = y`.
+// This is used to go between `memory_index` (source field order to memory order)
+// and `inverse_memory_index` (memory order to source field order).
+// See also `FieldsShape::Arbitrary::memory_index` for more details.
+// FIXME(eddyb) build a better abstraction for permutations, if possible.
+fn invert_mapping(map: &[u32]) -> Vec<u32> {
+ let mut inverse = vec![0; map.len()];
+ for i in 0..map.len() {
+ inverse[map[i] as usize] = i as u32;
+ }
+ inverse
+}
+
+pub trait LayoutCalculator {
+ type TargetDataLayoutRef: Borrow<TargetDataLayout>;
+
+ fn delay_bug(&self, txt: &str);
+ fn current_data_layout(&self) -> Self::TargetDataLayoutRef;
+
+ fn scalar_pair<V: Idx>(&self, a: Scalar, b: Scalar) -> LayoutS<V> {
+ let dl = self.current_data_layout();
+ let dl = dl.borrow();
+ let b_align = b.align(dl);
+ let align = a.align(dl).max(b_align).max(dl.aggregate_align);
+ let b_offset = a.size(dl).align_to(b_align.abi);
+ let size = (b_offset + b.size(dl)).align_to(align.abi);
+
+ // HACK(nox): We iter on `b` and then `a` because `max_by_key`
+ // returns the last maximum.
+ let largest_niche = Niche::from_scalar(dl, b_offset, b)
+ .into_iter()
+ .chain(Niche::from_scalar(dl, Size::ZERO, a))
+ .max_by_key(|niche| niche.available(dl));
+
+ LayoutS {
+ variants: Variants::Single { index: V::new(0) },
+ fields: FieldsShape::Arbitrary {
+ offsets: vec![Size::ZERO, b_offset],
+ memory_index: vec![0, 1],
+ },
+ abi: Abi::ScalarPair(a, b),
+ largest_niche,
+ align,
+ size,
+ }
+ }
+
+ fn univariant<'a, V: Idx, F: Deref<Target = &'a LayoutS<V>> + Debug>(
+ &self,
+ dl: &TargetDataLayout,
+ fields: &[F],
+ repr: &ReprOptions,
+ kind: StructKind,
+ ) -> Option<LayoutS<V>> {
+ let pack = repr.pack;
+ let mut align = if pack.is_some() { dl.i8_align } else { dl.aggregate_align };
+ let mut inverse_memory_index: Vec<u32> = (0..fields.len() as u32).collect();
+ let optimize = !repr.inhibit_struct_field_reordering_opt();
+ if optimize {
+ let end =
+ if let StructKind::MaybeUnsized = kind { fields.len() - 1 } else { fields.len() };
+ let optimizing = &mut inverse_memory_index[..end];
+ let effective_field_align = |f: &F| {
+ if let Some(pack) = pack {
+ // return the packed alignment in bytes
+ f.align.abi.min(pack).bytes()
+ } else {
+ // returns log2(effective-align).
+ // This is ok since `pack` applies to all fields equally.
+ // The calculation assumes that size is an integer multiple of align, except for ZSTs.
+ //
+ // group [u8; 4] with align-4 or [u8; 6] with align-2 fields
+ f.align.abi.bytes().max(f.size.bytes()).trailing_zeros() as u64
+ }
+ };
+
+ // If `-Z randomize-layout` was enabled for the type definition we can shuffle
+ // the field ordering to try and catch some code making assumptions about layouts
+ // we don't guarantee
+ if repr.can_randomize_type_layout() && cfg!(feature = "randomize") {
+ #[cfg(feature = "randomize")]
+ {
+ // `ReprOptions.layout_seed` is a deterministic seed that we can use to
+ // randomize field ordering with
+ let mut rng = Xoshiro128StarStar::seed_from_u64(repr.field_shuffle_seed);
+
+ // Shuffle the ordering of the fields
+ optimizing.shuffle(&mut rng);
+ }
+ // Otherwise we just leave things alone and actually optimize the type's fields
+ } else {
+ match kind {
+ StructKind::AlwaysSized | StructKind::MaybeUnsized => {
+ optimizing.sort_by_key(|&x| {
+ // Place ZSTs first to avoid "interesting offsets",
+ // especially with only one or two non-ZST fields.
+ // Then place largest alignments first, largest niches within an alignment group last
+ let f = &fields[x as usize];
+ let niche_size = f.largest_niche.map_or(0, |n| n.available(dl));
+ (!f.is_zst(), cmp::Reverse(effective_field_align(f)), niche_size)
+ });
+ }
+
+ StructKind::Prefixed(..) => {
+ // Sort in ascending alignment so that the layout stays optimal
+ // regardless of the prefix.
+ // And put the largest niche in an alignment group at the end
+ // so it can be used as discriminant in jagged enums
+ optimizing.sort_by_key(|&x| {
+ let f = &fields[x as usize];
+ let niche_size = f.largest_niche.map_or(0, |n| n.available(dl));
+ (effective_field_align(f), niche_size)
+ });
+ }
+ }
+
+ // FIXME(Kixiron): We can always shuffle fields within a given alignment class
+ // regardless of the status of `-Z randomize-layout`
+ }
+ }
+ // inverse_memory_index holds field indices by increasing memory offset.
+ // That is, if field 5 has offset 0, the first element of inverse_memory_index is 5.
+ // We now write field offsets to the corresponding offset slot;
+ // field 5 with offset 0 puts 0 in offsets[5].
+ // At the bottom of this function, we invert `inverse_memory_index` to
+ // produce `memory_index` (see `invert_mapping`).
+ let mut sized = true;
+ let mut offsets = vec![Size::ZERO; fields.len()];
+ let mut offset = Size::ZERO;
+ let mut largest_niche = None;
+ let mut largest_niche_available = 0;
+ if let StructKind::Prefixed(prefix_size, prefix_align) = kind {
+ let prefix_align =
+ if let Some(pack) = pack { prefix_align.min(pack) } else { prefix_align };
+ align = align.max(AbiAndPrefAlign::new(prefix_align));
+ offset = prefix_size.align_to(prefix_align);
+ }
+ for &i in &inverse_memory_index {
+ let field = &fields[i as usize];
+ if !sized {
+ self.delay_bug(&format!(
+ "univariant: field #{} comes after unsized field",
+ offsets.len(),
+ ));
+ }
+
+ if field.is_unsized() {
+ sized = false;
+ }
+
+ // Invariant: offset < dl.obj_size_bound() <= 1<<61
+ let field_align = if let Some(pack) = pack {
+ field.align.min(AbiAndPrefAlign::new(pack))
+ } else {
+ field.align
+ };
+ offset = offset.align_to(field_align.abi);
+ align = align.max(field_align);
+
+ debug!("univariant offset: {:?} field: {:#?}", offset, field);
+ offsets[i as usize] = offset;
+
+ if let Some(mut niche) = field.largest_niche {
+ let available = niche.available(dl);
+ if available > largest_niche_available {
+ largest_niche_available = available;
+ niche.offset += offset;
+ largest_niche = Some(niche);
+ }
+ }
+
+ offset = offset.checked_add(field.size, dl)?;
+ }
+ if let Some(repr_align) = repr.align {
+ align = align.max(AbiAndPrefAlign::new(repr_align));
+ }
+ debug!("univariant min_size: {:?}", offset);
+ let min_size = offset;
+ // As stated above, inverse_memory_index holds field indices by increasing offset.
+ // This makes it an already-sorted view of the offsets vec.
+ // To invert it, consider:
+ // If field 5 has offset 0, offsets[0] is 5, and memory_index[5] should be 0.
+ // Field 5 would be the first element, so memory_index is i:
+ // Note: if we didn't optimize, it's already right.
+ let memory_index =
+ if optimize { invert_mapping(&inverse_memory_index) } else { inverse_memory_index };
+ let size = min_size.align_to(align.abi);
+ let mut abi = Abi::Aggregate { sized };
+ // Unpack newtype ABIs and find scalar pairs.
+ if sized && size.bytes() > 0 {
+ // All other fields must be ZSTs.
+ let mut non_zst_fields = fields.iter().enumerate().filter(|&(_, f)| !f.is_zst());
+
+ match (non_zst_fields.next(), non_zst_fields.next(), non_zst_fields.next()) {
+ // We have exactly one non-ZST field.
+ (Some((i, field)), None, None) => {
+ // Field fills the struct and it has a scalar or scalar pair ABI.
+ if offsets[i].bytes() == 0 && align.abi == field.align.abi && size == field.size
+ {
+ match field.abi {
+ // For plain scalars, or vectors of them, we can't unpack
+ // newtypes for `#[repr(C)]`, as that affects C ABIs.
+ Abi::Scalar(_) | Abi::Vector { .. } if optimize => {
+ abi = field.abi;
+ }
+ // But scalar pairs are Rust-specific and get
+ // treated as aggregates by C ABIs anyway.
+ Abi::ScalarPair(..) => {
+ abi = field.abi;
+ }
+ _ => {}
+ }
+ }
+ }
+
+ // Two non-ZST fields, and they're both scalars.
+ (Some((i, a)), Some((j, b)), None) => {
+ match (a.abi, b.abi) {
+ (Abi::Scalar(a), Abi::Scalar(b)) => {
+ // Order by the memory placement, not source order.
+ let ((i, a), (j, b)) = if offsets[i] < offsets[j] {
+ ((i, a), (j, b))
+ } else {
+ ((j, b), (i, a))
+ };
+ let pair = self.scalar_pair::<V>(a, b);
+ let pair_offsets = match pair.fields {
+ FieldsShape::Arbitrary { ref offsets, ref memory_index } => {
+ assert_eq!(memory_index, &[0, 1]);
+ offsets
+ }
+ _ => panic!(),
+ };
+ if offsets[i] == pair_offsets[0]
+ && offsets[j] == pair_offsets[1]
+ && align == pair.align
+ && size == pair.size
+ {
+ // We can use `ScalarPair` only when it matches our
+ // already computed layout (including `#[repr(C)]`).
+ abi = pair.abi;
+ }
+ }
+ _ => {}
+ }
+ }
+
+ _ => {}
+ }
+ }
+ if fields.iter().any(|f| f.abi.is_uninhabited()) {
+ abi = Abi::Uninhabited;
+ }
+ Some(LayoutS {
+ variants: Variants::Single { index: V::new(0) },
+ fields: FieldsShape::Arbitrary { offsets, memory_index },
+ abi,
+ largest_niche,
+ align,
+ size,
+ })
+ }
+
+ fn layout_of_never_type<V: Idx>(&self) -> LayoutS<V> {
+ let dl = self.current_data_layout();
+ let dl = dl.borrow();
+ LayoutS {
+ variants: Variants::Single { index: V::new(0) },
+ fields: FieldsShape::Primitive,
+ abi: Abi::Uninhabited,
+ largest_niche: None,
+ align: dl.i8_align,
+ size: Size::ZERO,
+ }
+ }
+
+ fn layout_of_struct_or_enum<'a, V: Idx, F: Deref<Target = &'a LayoutS<V>> + Debug>(
+ &self,
+ repr: &ReprOptions,
+ variants: &IndexVec<V, Vec<F>>,
+ is_enum: bool,
+ is_unsafe_cell: bool,
+ scalar_valid_range: (Bound<u128>, Bound<u128>),
+ discr_range_of_repr: impl Fn(i128, i128) -> (Integer, bool),
+ discriminants: impl Iterator<Item = (V, i128)>,
+ niche_optimize_enum: bool,
+ always_sized: bool,
+ ) -> Option<LayoutS<V>> {
+ let dl = self.current_data_layout();
+ let dl = dl.borrow();
+
+ let scalar_unit = |value: Primitive| {
+ let size = value.size(dl);
+ assert!(size.bits() <= 128);
+ Scalar::Initialized { value, valid_range: WrappingRange::full(size) }
+ };
+
+ // A variant is absent if it's uninhabited and only has ZST fields.
+ // Present uninhabited variants only require space for their fields,
+ // but *not* an encoding of the discriminant (e.g., a tag value).
+ // See issue #49298 for more details on the need to leave space
+ // for non-ZST uninhabited data (mostly partial initialization).
+ let absent = |fields: &[F]| {
+ let uninhabited = fields.iter().any(|f| f.abi.is_uninhabited());
+ let is_zst = fields.iter().all(|f| f.is_zst());
+ uninhabited && is_zst
+ };
+ let (present_first, present_second) = {
+ let mut present_variants = variants
+ .iter_enumerated()
+ .filter_map(|(i, v)| if absent(v) { None } else { Some(i) });
+ (present_variants.next(), present_variants.next())
+ };
+ let present_first = match present_first {
+ Some(present_first) => present_first,
+ // Uninhabited because it has no variants, or only absent ones.
+ None if is_enum => {
+ return Some(self.layout_of_never_type());
+ }
+ // If it's a struct, still compute a layout so that we can still compute the
+ // field offsets.
+ None => V::new(0),
+ };
+
+ let is_struct = !is_enum ||
+ // Only one variant is present.
+ (present_second.is_none() &&
+ // Representation optimizations are allowed.
+ !repr.inhibit_enum_layout_opt());
+ if is_struct {
+ // Struct, or univariant enum equivalent to a struct.
+ // (Typechecking will reject discriminant-sizing attrs.)
+
+ let v = present_first;
+ let kind = if is_enum || variants[v].is_empty() {
+ StructKind::AlwaysSized
+ } else {
+ if !always_sized { StructKind::MaybeUnsized } else { StructKind::AlwaysSized }
+ };
+
+ let mut st = self.univariant(dl, &variants[v], repr, kind)?;
+ st.variants = Variants::Single { index: v };
+
+ if is_unsafe_cell {
+ let hide_niches = |scalar: &mut _| match scalar {
+ Scalar::Initialized { value, valid_range } => {
+ *valid_range = WrappingRange::full(value.size(dl))
+ }
+ // Already doesn't have any niches
+ Scalar::Union { .. } => {}
+ };
+ match &mut st.abi {
+ Abi::Uninhabited => {}
+ Abi::Scalar(scalar) => hide_niches(scalar),
+ Abi::ScalarPair(a, b) => {
+ hide_niches(a);
+ hide_niches(b);
+ }
+ Abi::Vector { element, count: _ } => hide_niches(element),
+ Abi::Aggregate { sized: _ } => {}
+ }
+ st.largest_niche = None;
+ return Some(st);
+ }
+
+ let (start, end) = scalar_valid_range;
+ match st.abi {
+ Abi::Scalar(ref mut scalar) | Abi::ScalarPair(ref mut scalar, _) => {
+ // Enlarging validity ranges would result in missed
+ // optimizations, *not* wrongly assuming the inner
+ // value is valid. e.g. unions already enlarge validity ranges,
+ // because the values may be uninitialized.
+ //
+ // Because of that we only check that the start and end
+ // of the range is representable with this scalar type.
+
+ let max_value = scalar.size(dl).unsigned_int_max();
+ if let Bound::Included(start) = start {
+ // FIXME(eddyb) this might be incorrect - it doesn't
+ // account for wrap-around (end < start) ranges.
+ assert!(start <= max_value, "{start} > {max_value}");
+ scalar.valid_range_mut().start = start;
+ }
+ if let Bound::Included(end) = end {
+ // FIXME(eddyb) this might be incorrect - it doesn't
+ // account for wrap-around (end < start) ranges.
+ assert!(end <= max_value, "{end} > {max_value}");
+ scalar.valid_range_mut().end = end;
+ }
+
+ // Update `largest_niche` if we have introduced a larger niche.
+ let niche = Niche::from_scalar(dl, Size::ZERO, *scalar);
+ if let Some(niche) = niche {
+ match st.largest_niche {
+ Some(largest_niche) => {
+ // Replace the existing niche even if they're equal,
+ // because this one is at a lower offset.
+ if largest_niche.available(dl) <= niche.available(dl) {
+ st.largest_niche = Some(niche);
+ }
+ }
+ None => st.largest_niche = Some(niche),
+ }
+ }
+ }
+ _ => assert!(
+ start == Bound::Unbounded && end == Bound::Unbounded,
+ "nonscalar layout for layout_scalar_valid_range type: {:#?}",
+ st,
+ ),
+ }
+
+ return Some(st);
+ }
+
+ // At this point, we have handled all unions and
+ // structs. (We have also handled univariant enums
+ // that allow representation optimization.)
+ assert!(is_enum);
+
+ // Until we've decided whether to use the tagged or
+ // niche filling LayoutS, we don't want to intern the
+ // variant layouts, so we can't store them in the
+ // overall LayoutS. Store the overall LayoutS
+ // and the variant LayoutSs here until then.
+ struct TmpLayout<V: Idx> {
+ layout: LayoutS<V>,
+ variants: IndexVec<V, LayoutS<V>>,
+ }
+
+ let calculate_niche_filling_layout = || -> Option<TmpLayout<V>> {
+ if niche_optimize_enum {
+ return None;
+ }
+
+ if variants.len() < 2 {
+ return None;
+ }
+
+ let mut align = dl.aggregate_align;
+ let mut variant_layouts = variants
+ .iter_enumerated()
+ .map(|(j, v)| {
+ let mut st = self.univariant(dl, v, repr, StructKind::AlwaysSized)?;
+ st.variants = Variants::Single { index: j };
+
+ align = align.max(st.align);
+
+ Some(st)
+ })
+ .collect::<Option<IndexVec<V, _>>>()?;
+
+ let largest_variant_index = variant_layouts
+ .iter_enumerated()
+ .max_by_key(|(_i, layout)| layout.size.bytes())
+ .map(|(i, _layout)| i)?;
+
+ let all_indices = (0..=variants.len() - 1).map(V::new);
+ let needs_disc = |index: V| index != largest_variant_index && !absent(&variants[index]);
+ let niche_variants = all_indices.clone().find(|v| needs_disc(*v)).unwrap().index()
+ ..=all_indices.rev().find(|v| needs_disc(*v)).unwrap().index();
+
+ let count = niche_variants.size_hint().1.unwrap() as u128;
+
+ // Find the field with the largest niche
+ let (field_index, niche, (niche_start, niche_scalar)) = variants[largest_variant_index]
+ .iter()
+ .enumerate()
+ .filter_map(|(j, field)| Some((j, field.largest_niche?)))
+ .max_by_key(|(_, niche)| niche.available(dl))
+ .and_then(|(j, niche)| Some((j, niche, niche.reserve(dl, count)?)))?;
+ let niche_offset =
+ niche.offset + variant_layouts[largest_variant_index].fields.offset(field_index);
+ let niche_size = niche.value.size(dl);
+ let size = variant_layouts[largest_variant_index].size.align_to(align.abi);
+
+ let all_variants_fit = variant_layouts.iter_enumerated_mut().all(|(i, layout)| {
+ if i == largest_variant_index {
+ return true;
+ }
+
+ layout.largest_niche = None;
+
+ if layout.size <= niche_offset {
+ // This variant will fit before the niche.
+ return true;
+ }
+
+ // Determine if it'll fit after the niche.
+ let this_align = layout.align.abi;
+ let this_offset = (niche_offset + niche_size).align_to(this_align);
+
+ if this_offset + layout.size > size {
+ return false;
+ }
+
+ // It'll fit, but we need to make some adjustments.
+ match layout.fields {
+ FieldsShape::Arbitrary { ref mut offsets, .. } => {
+ for (j, offset) in offsets.iter_mut().enumerate() {
+ if !variants[i][j].is_zst() {
+ *offset += this_offset;
+ }
+ }
+ }
+ _ => {
+ panic!("Layout of fields should be Arbitrary for variants")
+ }
+ }
+
+ // It can't be a Scalar or ScalarPair because the offset isn't 0.
+ if !layout.abi.is_uninhabited() {
+ layout.abi = Abi::Aggregate { sized: true };
+ }
+ layout.size += this_offset;
+
+ true
+ });
+
+ if !all_variants_fit {
+ return None;
+ }
+
+ let largest_niche = Niche::from_scalar(dl, niche_offset, niche_scalar);
+
+ let others_zst = variant_layouts
+ .iter_enumerated()
+ .all(|(i, layout)| i == largest_variant_index || layout.size == Size::ZERO);
+ let same_size = size == variant_layouts[largest_variant_index].size;
+ let same_align = align == variant_layouts[largest_variant_index].align;
+
+ let abi = if variant_layouts.iter().all(|v| v.abi.is_uninhabited()) {
+ Abi::Uninhabited
+ } else if same_size && same_align && others_zst {
+ match variant_layouts[largest_variant_index].abi {
+ // When the total alignment and size match, we can use the
+ // same ABI as the scalar variant with the reserved niche.
+ Abi::Scalar(_) => Abi::Scalar(niche_scalar),
+ Abi::ScalarPair(first, second) => {
+ // Only the niche is guaranteed to be initialised,
+ // so use union layouts for the other primitive.
+ if niche_offset == Size::ZERO {
+ Abi::ScalarPair(niche_scalar, second.to_union())
+ } else {
+ Abi::ScalarPair(first.to_union(), niche_scalar)
+ }
+ }
+ _ => Abi::Aggregate { sized: true },
+ }
+ } else {
+ Abi::Aggregate { sized: true }
+ };
+
+ let layout = LayoutS {
+ variants: Variants::Multiple {
+ tag: niche_scalar,
+ tag_encoding: TagEncoding::Niche {
+ untagged_variant: largest_variant_index,
+ niche_variants: (V::new(*niche_variants.start())
+ ..=V::new(*niche_variants.end())),
+ niche_start,
+ },
+ tag_field: 0,
+ variants: IndexVec::new(),
+ },
+ fields: FieldsShape::Arbitrary {
+ offsets: vec![niche_offset],
+ memory_index: vec![0],
+ },
+ abi,
+ largest_niche,
+ size,
+ align,
+ };
+
+ Some(TmpLayout { layout, variants: variant_layouts })
+ };
+
+ let niche_filling_layout = calculate_niche_filling_layout();
+
+ let (mut min, mut max) = (i128::MAX, i128::MIN);
+ let discr_type = repr.discr_type();
+ let bits = Integer::from_attr(dl, discr_type).size().bits();
+ for (i, mut val) in discriminants {
+ if variants[i].iter().any(|f| f.abi.is_uninhabited()) {
+ continue;
+ }
+ if discr_type.is_signed() {
+ // sign extend the raw representation to be an i128
+ val = (val << (128 - bits)) >> (128 - bits);
+ }
+ if val < min {
+ min = val;
+ }
+ if val > max {
+ max = val;
+ }
+ }
+ // We might have no inhabited variants, so pretend there's at least one.
+ if (min, max) == (i128::MAX, i128::MIN) {
+ min = 0;
+ max = 0;
+ }
+ assert!(min <= max, "discriminant range is {}...{}", min, max);
+ let (min_ity, signed) = discr_range_of_repr(min, max); //Integer::repr_discr(tcx, ty, &repr, min, max);
+
+ let mut align = dl.aggregate_align;
+ let mut size = Size::ZERO;
+
+ // We're interested in the smallest alignment, so start large.
+ let mut start_align = Align::from_bytes(256).unwrap();
+ assert_eq!(Integer::for_align(dl, start_align), None);
+
+ // repr(C) on an enum tells us to make a (tag, union) layout,
+ // so we need to grow the prefix alignment to be at least
+ // the alignment of the union. (This value is used both for
+ // determining the alignment of the overall enum, and the
+ // determining the alignment of the payload after the tag.)
+ let mut prefix_align = min_ity.align(dl).abi;
+ if repr.c() {
+ for fields in variants {
+ for field in fields {
+ prefix_align = prefix_align.max(field.align.abi);
+ }
+ }
+ }
+
+ // Create the set of structs that represent each variant.
+ let mut layout_variants = variants
+ .iter_enumerated()
+ .map(|(i, field_layouts)| {
+ let mut st = self.univariant(
+ dl,
+ field_layouts,
+ repr,
+ StructKind::Prefixed(min_ity.size(), prefix_align),
+ )?;
+ st.variants = Variants::Single { index: i };
+ // Find the first field we can't move later
+ // to make room for a larger discriminant.
+ for field in st.fields.index_by_increasing_offset().map(|j| &field_layouts[j]) {
+ if !field.is_zst() || field.align.abi.bytes() != 1 {
+ start_align = start_align.min(field.align.abi);
+ break;
+ }
+ }
+ size = cmp::max(size, st.size);
+ align = align.max(st.align);
+ Some(st)
+ })
+ .collect::<Option<IndexVec<V, _>>>()?;
+
+ // Align the maximum variant size to the largest alignment.
+ size = size.align_to(align.abi);
+
+ if size.bytes() >= dl.obj_size_bound() {
+ return None;
+ }
+
+ let typeck_ity = Integer::from_attr(dl, repr.discr_type());
+ if typeck_ity < min_ity {
+ // It is a bug if Layout decided on a greater discriminant size than typeck for
+ // some reason at this point (based on values discriminant can take on). Mostly
+ // because this discriminant will be loaded, and then stored into variable of
+ // type calculated by typeck. Consider such case (a bug): typeck decided on
+ // byte-sized discriminant, but layout thinks we need a 16-bit to store all
+ // discriminant values. That would be a bug, because then, in codegen, in order
+ // to store this 16-bit discriminant into 8-bit sized temporary some of the
+ // space necessary to represent would have to be discarded (or layout is wrong
+ // on thinking it needs 16 bits)
+ panic!(
+ "layout decided on a larger discriminant type ({:?}) than typeck ({:?})",
+ min_ity, typeck_ity
+ );
+ // However, it is fine to make discr type however large (as an optimisation)
+ // after this point – we’ll just truncate the value we load in codegen.
+ }
+
+ // Check to see if we should use a different type for the
+ // discriminant. We can safely use a type with the same size
+ // as the alignment of the first field of each variant.
+ // We increase the size of the discriminant to avoid LLVM copying
+ // padding when it doesn't need to. This normally causes unaligned
+ // load/stores and excessive memcpy/memset operations. By using a
+ // bigger integer size, LLVM can be sure about its contents and
+ // won't be so conservative.
+
+ // Use the initial field alignment
+ let mut ity = if repr.c() || repr.int.is_some() {
+ min_ity
+ } else {
+ Integer::for_align(dl, start_align).unwrap_or(min_ity)
+ };
+
+ // If the alignment is not larger than the chosen discriminant size,
+ // don't use the alignment as the final size.
+ if ity <= min_ity {
+ ity = min_ity;
+ } else {
+ // Patch up the variants' first few fields.
+ let old_ity_size = min_ity.size();
+ let new_ity_size = ity.size();
+ for variant in &mut layout_variants {
+ match variant.fields {
+ FieldsShape::Arbitrary { ref mut offsets, .. } => {
+ for i in offsets {
+ if *i <= old_ity_size {
+ assert_eq!(*i, old_ity_size);
+ *i = new_ity_size;
+ }
+ }
+ // We might be making the struct larger.
+ if variant.size <= old_ity_size {
+ variant.size = new_ity_size;
+ }
+ }
+ _ => panic!(),
+ }
+ }
+ }
+
+ let tag_mask = ity.size().unsigned_int_max();
+ let tag = Scalar::Initialized {
+ value: Int(ity, signed),
+ valid_range: WrappingRange {
+ start: (min as u128 & tag_mask),
+ end: (max as u128 & tag_mask),
+ },
+ };
+ let mut abi = Abi::Aggregate { sized: true };
+
+ if layout_variants.iter().all(|v| v.abi.is_uninhabited()) {
+ abi = Abi::Uninhabited;
+ } else if tag.size(dl) == size {
+ // Make sure we only use scalar layout when the enum is entirely its
+ // own tag (i.e. it has no padding nor any non-ZST variant fields).
+ abi = Abi::Scalar(tag);
+ } else {
+ // Try to use a ScalarPair for all tagged enums.
+ let mut common_prim = None;
+ let mut common_prim_initialized_in_all_variants = true;
+ for (field_layouts, layout_variant) in iter::zip(variants, &layout_variants) {
+ let FieldsShape::Arbitrary { ref offsets, .. } = layout_variant.fields else {
+ panic!();
+ };
+ let mut fields = iter::zip(field_layouts, offsets).filter(|p| !p.0.is_zst());
+ let (field, offset) = match (fields.next(), fields.next()) {
+ (None, None) => {
+ common_prim_initialized_in_all_variants = false;
+ continue;
+ }
+ (Some(pair), None) => pair,
+ _ => {
+ common_prim = None;
+ break;
+ }
+ };
+ let prim = match field.abi {
+ Abi::Scalar(scalar) => {
+ common_prim_initialized_in_all_variants &=
+ matches!(scalar, Scalar::Initialized { .. });
+ scalar.primitive()
+ }
+ _ => {
+ common_prim = None;
+ break;
+ }
+ };
+ if let Some(pair) = common_prim {
+ // This is pretty conservative. We could go fancier
+ // by conflating things like i32 and u32, or even
+ // realising that (u8, u8) could just cohabit with
+ // u16 or even u32.
+ if pair != (prim, offset) {
+ common_prim = None;
+ break;
+ }
+ } else {
+ common_prim = Some((prim, offset));
+ }
+ }
+ if let Some((prim, offset)) = common_prim {
+ let prim_scalar = if common_prim_initialized_in_all_variants {
+ scalar_unit(prim)
+ } else {
+ // Common prim might be uninit.
+ Scalar::Union { value: prim }
+ };
+ let pair = self.scalar_pair::<V>(tag, prim_scalar);
+ let pair_offsets = match pair.fields {
+ FieldsShape::Arbitrary { ref offsets, ref memory_index } => {
+ assert_eq!(memory_index, &[0, 1]);
+ offsets
+ }
+ _ => panic!(),
+ };
+ if pair_offsets[0] == Size::ZERO
+ && pair_offsets[1] == *offset
+ && align == pair.align
+ && size == pair.size
+ {
+ // We can use `ScalarPair` only when it matches our
+ // already computed layout (including `#[repr(C)]`).
+ abi = pair.abi;
+ }
+ }
+ }
+
+ // If we pick a "clever" (by-value) ABI, we might have to adjust the ABI of the
+ // variants to ensure they are consistent. This is because a downcast is
+ // semantically a NOP, and thus should not affect layout.
+ if matches!(abi, Abi::Scalar(..) | Abi::ScalarPair(..)) {
+ for variant in &mut layout_variants {
+ // We only do this for variants with fields; the others are not accessed anyway.
+ // Also do not overwrite any already existing "clever" ABIs.
+ if variant.fields.count() > 0 && matches!(variant.abi, Abi::Aggregate { .. }) {
+ variant.abi = abi;
+ // Also need to bump up the size and alignment, so that the entire value fits in here.
+ variant.size = cmp::max(variant.size, size);
+ variant.align.abi = cmp::max(variant.align.abi, align.abi);
+ }
+ }
+ }
+
+ let largest_niche = Niche::from_scalar(dl, Size::ZERO, tag);
+
+ let tagged_layout = LayoutS {
+ variants: Variants::Multiple {
+ tag,
+ tag_encoding: TagEncoding::Direct,
+ tag_field: 0,
+ variants: IndexVec::new(),
+ },
+ fields: FieldsShape::Arbitrary { offsets: vec![Size::ZERO], memory_index: vec![0] },
+ largest_niche,
+ abi,
+ align,
+ size,
+ };
+
+ let tagged_layout = TmpLayout { layout: tagged_layout, variants: layout_variants };
+
+ let mut best_layout = match (tagged_layout, niche_filling_layout) {
+ (tl, Some(nl)) => {
+ // Pick the smaller layout; otherwise,
+ // pick the layout with the larger niche; otherwise,
+ // pick tagged as it has simpler codegen.
+ use cmp::Ordering::*;
+ let niche_size = |tmp_l: &TmpLayout<V>| {
+ tmp_l.layout.largest_niche.map_or(0, |n| n.available(dl))
+ };
+ match (tl.layout.size.cmp(&nl.layout.size), niche_size(&tl).cmp(&niche_size(&nl))) {
+ (Greater, _) => nl,
+ (Equal, Less) => nl,
+ _ => tl,
+ }
+ }
+ (tl, None) => tl,
+ };
+
+ // Now we can intern the variant layouts and store them in the enum layout.
+ best_layout.layout.variants = match best_layout.layout.variants {
+ Variants::Multiple { tag, tag_encoding, tag_field, .. } => {
+ Variants::Multiple { tag, tag_encoding, tag_field, variants: best_layout.variants }
+ }
+ _ => panic!(),
+ };
+ Some(best_layout.layout)
+ }
+
+ fn layout_of_union<'a, V: Idx, F: Deref<Target = &'a LayoutS<V>> + Debug>(
+ &self,
+ repr: &ReprOptions,
+ variants: &IndexVec<V, Vec<F>>,
+ ) -> Option<LayoutS<V>> {
+ let dl = self.current_data_layout();
+ let dl = dl.borrow();
+ let mut align = if repr.pack.is_some() { dl.i8_align } else { dl.aggregate_align };
+
+ if let Some(repr_align) = repr.align {
+ align = align.max(AbiAndPrefAlign::new(repr_align));
+ }
+
+ let optimize = !repr.inhibit_union_abi_opt();
+ let mut size = Size::ZERO;
+ let mut abi = Abi::Aggregate { sized: true };
+ let index = V::new(0);
+ for field in &variants[index] {
+ assert!(field.is_sized());
+ align = align.max(field.align);
+
+ // If all non-ZST fields have the same ABI, forward this ABI
+ if optimize && !field.is_zst() {
+ // Discard valid range information and allow undef
+ let field_abi = match field.abi {
+ Abi::Scalar(x) => Abi::Scalar(x.to_union()),
+ Abi::ScalarPair(x, y) => Abi::ScalarPair(x.to_union(), y.to_union()),
+ Abi::Vector { element: x, count } => {
+ Abi::Vector { element: x.to_union(), count }
+ }
+ Abi::Uninhabited | Abi::Aggregate { .. } => Abi::Aggregate { sized: true },
+ };
+
+ if size == Size::ZERO {
+ // first non ZST: initialize 'abi'
+ abi = field_abi;
+ } else if abi != field_abi {
+ // different fields have different ABI: reset to Aggregate
+ abi = Abi::Aggregate { sized: true };
+ }
+ }
+
+ size = cmp::max(size, field.size);
+ }
+
+ if let Some(pack) = repr.pack {
+ align = align.min(AbiAndPrefAlign::new(pack));
+ }
+
+ Some(LayoutS {
+ variants: Variants::Single { index },
+ fields: FieldsShape::Union(NonZeroUsize::new(variants[index].len())?),
+ abi,
+ largest_niche: None,
+ align,
+ size: size.align_to(align.abi),
+ })
+ }
+}
diff --git a/compiler/rustc_abi/src/lib.rs b/compiler/rustc_abi/src/lib.rs
new file mode 100644
index 000000000..e14c9ea9a
--- /dev/null
+++ b/compiler/rustc_abi/src/lib.rs
@@ -0,0 +1,1502 @@
+#![cfg_attr(feature = "nightly", feature(step_trait, rustc_attrs, min_specialization))]
+
+use std::convert::{TryFrom, TryInto};
+use std::fmt;
+#[cfg(feature = "nightly")]
+use std::iter::Step;
+use std::num::{NonZeroUsize, ParseIntError};
+use std::ops::{Add, AddAssign, Mul, RangeInclusive, Sub};
+use std::str::FromStr;
+
+use bitflags::bitflags;
+#[cfg(feature = "nightly")]
+use rustc_data_structures::stable_hasher::StableOrd;
+use rustc_index::vec::{Idx, IndexVec};
+#[cfg(feature = "nightly")]
+use rustc_macros::HashStable_Generic;
+#[cfg(feature = "nightly")]
+use rustc_macros::{Decodable, Encodable};
+
+mod layout;
+
+pub use layout::LayoutCalculator;
+
+/// Requirements for a `StableHashingContext` to be used in this crate.
+/// This is a hack to allow using the `HashStable_Generic` derive macro
+/// instead of implementing everything in `rustc_middle`.
+pub trait HashStableContext {}
+
+use Integer::*;
+use Primitive::*;
+
+bitflags! {
+ #[derive(Default)]
+ #[cfg_attr(feature = "nightly", derive(Encodable, Decodable, HashStable_Generic))]
+ pub struct ReprFlags: u8 {
+ const IS_C = 1 << 0;
+ const IS_SIMD = 1 << 1;
+ const IS_TRANSPARENT = 1 << 2;
+ // Internal only for now. If true, don't reorder fields.
+ const IS_LINEAR = 1 << 3;
+ // If true, the type's layout can be randomized using
+ // the seed stored in `ReprOptions.layout_seed`
+ const RANDOMIZE_LAYOUT = 1 << 4;
+ // Any of these flags being set prevent field reordering optimisation.
+ const IS_UNOPTIMISABLE = ReprFlags::IS_C.bits
+ | ReprFlags::IS_SIMD.bits
+ | ReprFlags::IS_LINEAR.bits;
+ }
+}
+
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+#[cfg_attr(feature = "nightly", derive(Encodable, Decodable, HashStable_Generic))]
+pub enum IntegerType {
+ /// Pointer sized integer type, i.e. isize and usize. The field shows signedness, that
+ /// is, `Pointer(true)` is isize.
+ Pointer(bool),
+ /// Fix sized integer type, e.g. i8, u32, i128 The bool field shows signedness, `Fixed(I8, false)` means `u8`
+ Fixed(Integer, bool),
+}
+
+impl IntegerType {
+ pub fn is_signed(&self) -> bool {
+ match self {
+ IntegerType::Pointer(b) => *b,
+ IntegerType::Fixed(_, b) => *b,
+ }
+ }
+}
+
+/// Represents the repr options provided by the user,
+#[derive(Copy, Clone, Debug, Eq, PartialEq, Default)]
+#[cfg_attr(feature = "nightly", derive(Encodable, Decodable, HashStable_Generic))]
+pub struct ReprOptions {
+ pub int: Option<IntegerType>,
+ pub align: Option<Align>,
+ pub pack: Option<Align>,
+ pub flags: ReprFlags,
+ /// The seed to be used for randomizing a type's layout
+ ///
+ /// Note: This could technically be a `[u8; 16]` (a `u128`) which would
+ /// be the "most accurate" hash as it'd encompass the item and crate
+ /// hash without loss, but it does pay the price of being larger.
+ /// Everything's a tradeoff, a `u64` seed should be sufficient for our
+ /// purposes (primarily `-Z randomize-layout`)
+ pub field_shuffle_seed: u64,
+}
+
+impl ReprOptions {
+ #[inline]
+ pub fn simd(&self) -> bool {
+ self.flags.contains(ReprFlags::IS_SIMD)
+ }
+
+ #[inline]
+ pub fn c(&self) -> bool {
+ self.flags.contains(ReprFlags::IS_C)
+ }
+
+ #[inline]
+ pub fn packed(&self) -> bool {
+ self.pack.is_some()
+ }
+
+ #[inline]
+ pub fn transparent(&self) -> bool {
+ self.flags.contains(ReprFlags::IS_TRANSPARENT)
+ }
+
+ #[inline]
+ pub fn linear(&self) -> bool {
+ self.flags.contains(ReprFlags::IS_LINEAR)
+ }
+
+ /// Returns the discriminant type, given these `repr` options.
+ /// This must only be called on enums!
+ pub fn discr_type(&self) -> IntegerType {
+ self.int.unwrap_or(IntegerType::Pointer(true))
+ }
+
+ /// Returns `true` if this `#[repr()]` should inhabit "smart enum
+ /// layout" optimizations, such as representing `Foo<&T>` as a
+ /// single pointer.
+ pub fn inhibit_enum_layout_opt(&self) -> bool {
+ self.c() || self.int.is_some()
+ }
+
+ /// Returns `true` if this `#[repr()]` should inhibit struct field reordering
+ /// optimizations, such as with `repr(C)`, `repr(packed(1))`, or `repr(<int>)`.
+ pub fn inhibit_struct_field_reordering_opt(&self) -> bool {
+ if let Some(pack) = self.pack {
+ if pack.bytes() == 1 {
+ return true;
+ }
+ }
+
+ self.flags.intersects(ReprFlags::IS_UNOPTIMISABLE) || self.int.is_some()
+ }
+
+ /// Returns `true` if this type is valid for reordering and `-Z randomize-layout`
+ /// was enabled for its declaration crate
+ pub fn can_randomize_type_layout(&self) -> bool {
+ !self.inhibit_struct_field_reordering_opt()
+ && self.flags.contains(ReprFlags::RANDOMIZE_LAYOUT)
+ }
+
+ /// Returns `true` if this `#[repr()]` should inhibit union ABI optimisations.
+ pub fn inhibit_union_abi_opt(&self) -> bool {
+ self.c()
+ }
+}
+
+/// Parsed [Data layout](https://llvm.org/docs/LangRef.html#data-layout)
+/// for a target, which contains everything needed to compute layouts.
+#[derive(Debug, PartialEq, Eq)]
+pub struct TargetDataLayout {
+ pub endian: Endian,
+ pub i1_align: AbiAndPrefAlign,
+ pub i8_align: AbiAndPrefAlign,
+ pub i16_align: AbiAndPrefAlign,
+ pub i32_align: AbiAndPrefAlign,
+ pub i64_align: AbiAndPrefAlign,
+ pub i128_align: AbiAndPrefAlign,
+ pub f32_align: AbiAndPrefAlign,
+ pub f64_align: AbiAndPrefAlign,
+ pub pointer_size: Size,
+ pub pointer_align: AbiAndPrefAlign,
+ pub aggregate_align: AbiAndPrefAlign,
+
+ /// Alignments for vector types.
+ pub vector_align: Vec<(Size, AbiAndPrefAlign)>,
+
+ pub instruction_address_space: AddressSpace,
+
+ /// Minimum size of #[repr(C)] enums (default I32 bits)
+ pub c_enum_min_size: Integer,
+}
+
+impl Default for TargetDataLayout {
+ /// Creates an instance of `TargetDataLayout`.
+ fn default() -> TargetDataLayout {
+ let align = |bits| Align::from_bits(bits).unwrap();
+ TargetDataLayout {
+ endian: Endian::Big,
+ i1_align: AbiAndPrefAlign::new(align(8)),
+ i8_align: AbiAndPrefAlign::new(align(8)),
+ i16_align: AbiAndPrefAlign::new(align(16)),
+ i32_align: AbiAndPrefAlign::new(align(32)),
+ i64_align: AbiAndPrefAlign { abi: align(32), pref: align(64) },
+ i128_align: AbiAndPrefAlign { abi: align(32), pref: align(64) },
+ f32_align: AbiAndPrefAlign::new(align(32)),
+ f64_align: AbiAndPrefAlign::new(align(64)),
+ pointer_size: Size::from_bits(64),
+ pointer_align: AbiAndPrefAlign::new(align(64)),
+ aggregate_align: AbiAndPrefAlign { abi: align(0), pref: align(64) },
+ vector_align: vec![
+ (Size::from_bits(64), AbiAndPrefAlign::new(align(64))),
+ (Size::from_bits(128), AbiAndPrefAlign::new(align(128))),
+ ],
+ instruction_address_space: AddressSpace::DATA,
+ c_enum_min_size: Integer::I32,
+ }
+ }
+}
+
+pub enum TargetDataLayoutErrors<'a> {
+ InvalidAddressSpace { addr_space: &'a str, cause: &'a str, err: ParseIntError },
+ InvalidBits { kind: &'a str, bit: &'a str, cause: &'a str, err: ParseIntError },
+ MissingAlignment { cause: &'a str },
+ InvalidAlignment { cause: &'a str, err: String },
+ InconsistentTargetArchitecture { dl: &'a str, target: &'a str },
+ InconsistentTargetPointerWidth { pointer_size: u64, target: u32 },
+ InvalidBitsSize { err: String },
+}
+
+impl TargetDataLayout {
+ /// Parse data layout from an [llvm data layout string](https://llvm.org/docs/LangRef.html#data-layout)
+ ///
+ /// This function doesn't fill `c_enum_min_size` and it will always be `I32` since it can not be
+ /// determined from llvm string.
+ pub fn parse_from_llvm_datalayout_string<'a>(
+ input: &'a str,
+ ) -> Result<TargetDataLayout, TargetDataLayoutErrors<'a>> {
+ // Parse an address space index from a string.
+ let parse_address_space = |s: &'a str, cause: &'a str| {
+ s.parse::<u32>().map(AddressSpace).map_err(|err| {
+ TargetDataLayoutErrors::InvalidAddressSpace { addr_space: s, cause, err }
+ })
+ };
+
+ // Parse a bit count from a string.
+ let parse_bits = |s: &'a str, kind: &'a str, cause: &'a str| {
+ s.parse::<u64>().map_err(|err| TargetDataLayoutErrors::InvalidBits {
+ kind,
+ bit: s,
+ cause,
+ err,
+ })
+ };
+
+ // Parse a size string.
+ let size = |s: &'a str, cause: &'a str| parse_bits(s, "size", cause).map(Size::from_bits);
+
+ // Parse an alignment string.
+ let align = |s: &[&'a str], cause: &'a str| {
+ if s.is_empty() {
+ return Err(TargetDataLayoutErrors::MissingAlignment { cause });
+ }
+ let align_from_bits = |bits| {
+ Align::from_bits(bits)
+ .map_err(|err| TargetDataLayoutErrors::InvalidAlignment { cause, err })
+ };
+ let abi = parse_bits(s[0], "alignment", cause)?;
+ let pref = s.get(1).map_or(Ok(abi), |pref| parse_bits(pref, "alignment", cause))?;
+ Ok(AbiAndPrefAlign { abi: align_from_bits(abi)?, pref: align_from_bits(pref)? })
+ };
+
+ let mut dl = TargetDataLayout::default();
+ let mut i128_align_src = 64;
+ for spec in input.split('-') {
+ let spec_parts = spec.split(':').collect::<Vec<_>>();
+
+ match &*spec_parts {
+ ["e"] => dl.endian = Endian::Little,
+ ["E"] => dl.endian = Endian::Big,
+ [p] if p.starts_with('P') => {
+ dl.instruction_address_space = parse_address_space(&p[1..], "P")?
+ }
+ ["a", ref a @ ..] => dl.aggregate_align = align(a, "a")?,
+ ["f32", ref a @ ..] => dl.f32_align = align(a, "f32")?,
+ ["f64", ref a @ ..] => dl.f64_align = align(a, "f64")?,
+ [p @ "p", s, ref a @ ..] | [p @ "p0", s, ref a @ ..] => {
+ dl.pointer_size = size(s, p)?;
+ dl.pointer_align = align(a, p)?;
+ }
+ [s, ref a @ ..] if s.starts_with('i') => {
+ let Ok(bits) = s[1..].parse::<u64>() else {
+ size(&s[1..], "i")?; // For the user error.
+ continue;
+ };
+ let a = align(a, s)?;
+ match bits {
+ 1 => dl.i1_align = a,
+ 8 => dl.i8_align = a,
+ 16 => dl.i16_align = a,
+ 32 => dl.i32_align = a,
+ 64 => dl.i64_align = a,
+ _ => {}
+ }
+ if bits >= i128_align_src && bits <= 128 {
+ // Default alignment for i128 is decided by taking the alignment of
+ // largest-sized i{64..=128}.
+ i128_align_src = bits;
+ dl.i128_align = a;
+ }
+ }
+ [s, ref a @ ..] if s.starts_with('v') => {
+ let v_size = size(&s[1..], "v")?;
+ let a = align(a, s)?;
+ if let Some(v) = dl.vector_align.iter_mut().find(|v| v.0 == v_size) {
+ v.1 = a;
+ continue;
+ }
+ // No existing entry, add a new one.
+ dl.vector_align.push((v_size, a));
+ }
+ _ => {} // Ignore everything else.
+ }
+ }
+ Ok(dl)
+ }
+
+ /// Returns exclusive upper bound on object size.
+ ///
+ /// The theoretical maximum object size is defined as the maximum positive `isize` value.
+ /// This ensures that the `offset` semantics remain well-defined by allowing it to correctly
+ /// index every address within an object along with one byte past the end, along with allowing
+ /// `isize` to store the difference between any two pointers into an object.
+ ///
+ /// The upper bound on 64-bit currently needs to be lower because LLVM uses a 64-bit integer
+ /// to represent object size in bits. It would need to be 1 << 61 to account for this, but is
+ /// currently conservatively bounded to 1 << 47 as that is enough to cover the current usable
+ /// address space on 64-bit ARMv8 and x86_64.
+ #[inline]
+ pub fn obj_size_bound(&self) -> u64 {
+ match self.pointer_size.bits() {
+ 16 => 1 << 15,
+ 32 => 1 << 31,
+ 64 => 1 << 47,
+ bits => panic!("obj_size_bound: unknown pointer bit size {}", bits),
+ }
+ }
+
+ #[inline]
+ pub fn ptr_sized_integer(&self) -> Integer {
+ match self.pointer_size.bits() {
+ 16 => I16,
+ 32 => I32,
+ 64 => I64,
+ bits => panic!("ptr_sized_integer: unknown pointer bit size {}", bits),
+ }
+ }
+
+ #[inline]
+ pub fn vector_align(&self, vec_size: Size) -> AbiAndPrefAlign {
+ for &(size, align) in &self.vector_align {
+ if size == vec_size {
+ return align;
+ }
+ }
+ // Default to natural alignment, which is what LLVM does.
+ // That is, use the size, rounded up to a power of 2.
+ AbiAndPrefAlign::new(Align::from_bytes(vec_size.bytes().next_power_of_two()).unwrap())
+ }
+}
+
+pub trait HasDataLayout {
+ fn data_layout(&self) -> &TargetDataLayout;
+}
+
+impl HasDataLayout for TargetDataLayout {
+ #[inline]
+ fn data_layout(&self) -> &TargetDataLayout {
+ self
+ }
+}
+
+/// Endianness of the target, which must match cfg(target-endian).
+#[derive(Copy, Clone, PartialEq, Eq)]
+pub enum Endian {
+ Little,
+ Big,
+}
+
+impl Endian {
+ pub fn as_str(&self) -> &'static str {
+ match self {
+ Self::Little => "little",
+ Self::Big => "big",
+ }
+ }
+}
+
+impl fmt::Debug for Endian {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ f.write_str(self.as_str())
+ }
+}
+
+impl FromStr for Endian {
+ type Err = String;
+
+ fn from_str(s: &str) -> Result<Self, Self::Err> {
+ match s {
+ "little" => Ok(Self::Little),
+ "big" => Ok(Self::Big),
+ _ => Err(format!(r#"unknown endian: "{}""#, s)),
+ }
+ }
+}
+
+/// Size of a type in bytes.
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[cfg_attr(feature = "nightly", derive(Encodable, Decodable, HashStable_Generic))]
+pub struct Size {
+ raw: u64,
+}
+
+// Safety: Ord is implement as just comparing numerical values and numerical values
+// are not changed by (de-)serialization.
+#[cfg(feature = "nightly")]
+unsafe impl StableOrd for Size {}
+
+// This is debug-printed a lot in larger structs, don't waste too much space there
+impl fmt::Debug for Size {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ write!(f, "Size({} bytes)", self.bytes())
+ }
+}
+
+impl Size {
+ pub const ZERO: Size = Size { raw: 0 };
+
+ /// Rounds `bits` up to the next-higher byte boundary, if `bits` is
+ /// not a multiple of 8.
+ pub fn from_bits(bits: impl TryInto<u64>) -> Size {
+ let bits = bits.try_into().ok().unwrap();
+ // Avoid potential overflow from `bits + 7`.
+ Size { raw: bits / 8 + ((bits % 8) + 7) / 8 }
+ }
+
+ #[inline]
+ pub fn from_bytes(bytes: impl TryInto<u64>) -> Size {
+ let bytes: u64 = bytes.try_into().ok().unwrap();
+ Size { raw: bytes }
+ }
+
+ #[inline]
+ pub fn bytes(self) -> u64 {
+ self.raw
+ }
+
+ #[inline]
+ pub fn bytes_usize(self) -> usize {
+ self.bytes().try_into().unwrap()
+ }
+
+ #[inline]
+ pub fn bits(self) -> u64 {
+ #[cold]
+ fn overflow(bytes: u64) -> ! {
+ panic!("Size::bits: {} bytes in bits doesn't fit in u64", bytes)
+ }
+
+ self.bytes().checked_mul(8).unwrap_or_else(|| overflow(self.bytes()))
+ }
+
+ #[inline]
+ pub fn bits_usize(self) -> usize {
+ self.bits().try_into().unwrap()
+ }
+
+ #[inline]
+ pub fn align_to(self, align: Align) -> Size {
+ let mask = align.bytes() - 1;
+ Size::from_bytes((self.bytes() + mask) & !mask)
+ }
+
+ #[inline]
+ pub fn is_aligned(self, align: Align) -> bool {
+ let mask = align.bytes() - 1;
+ self.bytes() & mask == 0
+ }
+
+ #[inline]
+ pub fn checked_add<C: HasDataLayout>(self, offset: Size, cx: &C) -> Option<Size> {
+ let dl = cx.data_layout();
+
+ let bytes = self.bytes().checked_add(offset.bytes())?;
+
+ if bytes < dl.obj_size_bound() { Some(Size::from_bytes(bytes)) } else { None }
+ }
+
+ #[inline]
+ pub fn checked_mul<C: HasDataLayout>(self, count: u64, cx: &C) -> Option<Size> {
+ let dl = cx.data_layout();
+
+ let bytes = self.bytes().checked_mul(count)?;
+ if bytes < dl.obj_size_bound() { Some(Size::from_bytes(bytes)) } else { None }
+ }
+
+ /// Truncates `value` to `self` bits and then sign-extends it to 128 bits
+ /// (i.e., if it is negative, fill with 1's on the left).
+ #[inline]
+ pub fn sign_extend(self, value: u128) -> u128 {
+ let size = self.bits();
+ if size == 0 {
+ // Truncated until nothing is left.
+ return 0;
+ }
+ // Sign-extend it.
+ let shift = 128 - size;
+ // Shift the unsigned value to the left, then shift back to the right as signed
+ // (essentially fills with sign bit on the left).
+ (((value << shift) as i128) >> shift) as u128
+ }
+
+ /// Truncates `value` to `self` bits.
+ #[inline]
+ pub fn truncate(self, value: u128) -> u128 {
+ let size = self.bits();
+ if size == 0 {
+ // Truncated until nothing is left.
+ return 0;
+ }
+ let shift = 128 - size;
+ // Truncate (shift left to drop out leftover values, shift right to fill with zeroes).
+ (value << shift) >> shift
+ }
+
+ #[inline]
+ pub fn signed_int_min(&self) -> i128 {
+ self.sign_extend(1_u128 << (self.bits() - 1)) as i128
+ }
+
+ #[inline]
+ pub fn signed_int_max(&self) -> i128 {
+ i128::MAX >> (128 - self.bits())
+ }
+
+ #[inline]
+ pub fn unsigned_int_max(&self) -> u128 {
+ u128::MAX >> (128 - self.bits())
+ }
+}
+
+// Panicking addition, subtraction and multiplication for convenience.
+// Avoid during layout computation, return `LayoutError` instead.
+
+impl Add for Size {
+ type Output = Size;
+ #[inline]
+ fn add(self, other: Size) -> Size {
+ Size::from_bytes(self.bytes().checked_add(other.bytes()).unwrap_or_else(|| {
+ panic!("Size::add: {} + {} doesn't fit in u64", self.bytes(), other.bytes())
+ }))
+ }
+}
+
+impl Sub for Size {
+ type Output = Size;
+ #[inline]
+ fn sub(self, other: Size) -> Size {
+ Size::from_bytes(self.bytes().checked_sub(other.bytes()).unwrap_or_else(|| {
+ panic!("Size::sub: {} - {} would result in negative size", self.bytes(), other.bytes())
+ }))
+ }
+}
+
+impl Mul<Size> for u64 {
+ type Output = Size;
+ #[inline]
+ fn mul(self, size: Size) -> Size {
+ size * self
+ }
+}
+
+impl Mul<u64> for Size {
+ type Output = Size;
+ #[inline]
+ fn mul(self, count: u64) -> Size {
+ match self.bytes().checked_mul(count) {
+ Some(bytes) => Size::from_bytes(bytes),
+ None => panic!("Size::mul: {} * {} doesn't fit in u64", self.bytes(), count),
+ }
+ }
+}
+
+impl AddAssign for Size {
+ #[inline]
+ fn add_assign(&mut self, other: Size) {
+ *self = *self + other;
+ }
+}
+
+#[cfg(feature = "nightly")]
+impl Step for Size {
+ #[inline]
+ fn steps_between(start: &Self, end: &Self) -> Option<usize> {
+ u64::steps_between(&start.bytes(), &end.bytes())
+ }
+
+ #[inline]
+ fn forward_checked(start: Self, count: usize) -> Option<Self> {
+ u64::forward_checked(start.bytes(), count).map(Self::from_bytes)
+ }
+
+ #[inline]
+ fn forward(start: Self, count: usize) -> Self {
+ Self::from_bytes(u64::forward(start.bytes(), count))
+ }
+
+ #[inline]
+ unsafe fn forward_unchecked(start: Self, count: usize) -> Self {
+ Self::from_bytes(u64::forward_unchecked(start.bytes(), count))
+ }
+
+ #[inline]
+ fn backward_checked(start: Self, count: usize) -> Option<Self> {
+ u64::backward_checked(start.bytes(), count).map(Self::from_bytes)
+ }
+
+ #[inline]
+ fn backward(start: Self, count: usize) -> Self {
+ Self::from_bytes(u64::backward(start.bytes(), count))
+ }
+
+ #[inline]
+ unsafe fn backward_unchecked(start: Self, count: usize) -> Self {
+ Self::from_bytes(u64::backward_unchecked(start.bytes(), count))
+ }
+}
+
+/// Alignment of a type in bytes (always a power of two).
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[cfg_attr(feature = "nightly", derive(Encodable, Decodable, HashStable_Generic))]
+pub struct Align {
+ pow2: u8,
+}
+
+// This is debug-printed a lot in larger structs, don't waste too much space there
+impl fmt::Debug for Align {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ write!(f, "Align({} bytes)", self.bytes())
+ }
+}
+
+impl Align {
+ pub const ONE: Align = Align { pow2: 0 };
+ pub const MAX: Align = Align { pow2: 29 };
+
+ #[inline]
+ pub fn from_bits(bits: u64) -> Result<Align, String> {
+ Align::from_bytes(Size::from_bits(bits).bytes())
+ }
+
+ #[inline]
+ pub fn from_bytes(align: u64) -> Result<Align, String> {
+ // Treat an alignment of 0 bytes like 1-byte alignment.
+ if align == 0 {
+ return Ok(Align::ONE);
+ }
+
+ #[cold]
+ fn not_power_of_2(align: u64) -> String {
+ format!("`{}` is not a power of 2", align)
+ }
+
+ #[cold]
+ fn too_large(align: u64) -> String {
+ format!("`{}` is too large", align)
+ }
+
+ let mut bytes = align;
+ let mut pow2: u8 = 0;
+ while (bytes & 1) == 0 {
+ pow2 += 1;
+ bytes >>= 1;
+ }
+ if bytes != 1 {
+ return Err(not_power_of_2(align));
+ }
+ if pow2 > Self::MAX.pow2 {
+ return Err(too_large(align));
+ }
+
+ Ok(Align { pow2 })
+ }
+
+ #[inline]
+ pub fn bytes(self) -> u64 {
+ 1 << self.pow2
+ }
+
+ #[inline]
+ pub fn bits(self) -> u64 {
+ self.bytes() * 8
+ }
+
+ /// Computes the best alignment possible for the given offset
+ /// (the largest power of two that the offset is a multiple of).
+ ///
+ /// N.B., for an offset of `0`, this happens to return `2^64`.
+ #[inline]
+ pub fn max_for_offset(offset: Size) -> Align {
+ Align { pow2: offset.bytes().trailing_zeros() as u8 }
+ }
+
+ /// Lower the alignment, if necessary, such that the given offset
+ /// is aligned to it (the offset is a multiple of the alignment).
+ #[inline]
+ pub fn restrict_for_offset(self, offset: Size) -> Align {
+ self.min(Align::max_for_offset(offset))
+ }
+}
+
+/// A pair of alignments, ABI-mandated and preferred.
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+
+pub struct AbiAndPrefAlign {
+ pub abi: Align,
+ pub pref: Align,
+}
+
+impl AbiAndPrefAlign {
+ #[inline]
+ pub fn new(align: Align) -> AbiAndPrefAlign {
+ AbiAndPrefAlign { abi: align, pref: align }
+ }
+
+ #[inline]
+ pub fn min(self, other: AbiAndPrefAlign) -> AbiAndPrefAlign {
+ AbiAndPrefAlign { abi: self.abi.min(other.abi), pref: self.pref.min(other.pref) }
+ }
+
+ #[inline]
+ pub fn max(self, other: AbiAndPrefAlign) -> AbiAndPrefAlign {
+ AbiAndPrefAlign { abi: self.abi.max(other.abi), pref: self.pref.max(other.pref) }
+ }
+}
+
+/// Integers, also used for enum discriminants.
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
+#[cfg_attr(feature = "nightly", derive(Encodable, Decodable, HashStable_Generic))]
+
+pub enum Integer {
+ I8,
+ I16,
+ I32,
+ I64,
+ I128,
+}
+
+impl Integer {
+ #[inline]
+ pub fn size(self) -> Size {
+ match self {
+ I8 => Size::from_bytes(1),
+ I16 => Size::from_bytes(2),
+ I32 => Size::from_bytes(4),
+ I64 => Size::from_bytes(8),
+ I128 => Size::from_bytes(16),
+ }
+ }
+
+ /// Gets the Integer type from an IntegerType.
+ pub fn from_attr<C: HasDataLayout>(cx: &C, ity: IntegerType) -> Integer {
+ let dl = cx.data_layout();
+
+ match ity {
+ IntegerType::Pointer(_) => dl.ptr_sized_integer(),
+ IntegerType::Fixed(x, _) => x,
+ }
+ }
+
+ pub fn align<C: HasDataLayout>(self, cx: &C) -> AbiAndPrefAlign {
+ let dl = cx.data_layout();
+
+ match self {
+ I8 => dl.i8_align,
+ I16 => dl.i16_align,
+ I32 => dl.i32_align,
+ I64 => dl.i64_align,
+ I128 => dl.i128_align,
+ }
+ }
+
+ /// Finds the smallest Integer type which can represent the signed value.
+ #[inline]
+ pub fn fit_signed(x: i128) -> Integer {
+ match x {
+ -0x0000_0000_0000_0080..=0x0000_0000_0000_007f => I8,
+ -0x0000_0000_0000_8000..=0x0000_0000_0000_7fff => I16,
+ -0x0000_0000_8000_0000..=0x0000_0000_7fff_ffff => I32,
+ -0x8000_0000_0000_0000..=0x7fff_ffff_ffff_ffff => I64,
+ _ => I128,
+ }
+ }
+
+ /// Finds the smallest Integer type which can represent the unsigned value.
+ #[inline]
+ pub fn fit_unsigned(x: u128) -> Integer {
+ match x {
+ 0..=0x0000_0000_0000_00ff => I8,
+ 0..=0x0000_0000_0000_ffff => I16,
+ 0..=0x0000_0000_ffff_ffff => I32,
+ 0..=0xffff_ffff_ffff_ffff => I64,
+ _ => I128,
+ }
+ }
+
+ /// Finds the smallest integer with the given alignment.
+ pub fn for_align<C: HasDataLayout>(cx: &C, wanted: Align) -> Option<Integer> {
+ let dl = cx.data_layout();
+
+ for candidate in [I8, I16, I32, I64, I128] {
+ if wanted == candidate.align(dl).abi && wanted.bytes() == candidate.size().bytes() {
+ return Some(candidate);
+ }
+ }
+ None
+ }
+
+ /// Find the largest integer with the given alignment or less.
+ pub fn approximate_align<C: HasDataLayout>(cx: &C, wanted: Align) -> Integer {
+ let dl = cx.data_layout();
+
+ // FIXME(eddyb) maybe include I128 in the future, when it works everywhere.
+ for candidate in [I64, I32, I16] {
+ if wanted >= candidate.align(dl).abi && wanted.bytes() >= candidate.size().bytes() {
+ return candidate;
+ }
+ }
+ I8
+ }
+
+ // FIXME(eddyb) consolidate this and other methods that find the appropriate
+ // `Integer` given some requirements.
+ #[inline]
+ pub fn from_size(size: Size) -> Result<Self, String> {
+ match size.bits() {
+ 8 => Ok(Integer::I8),
+ 16 => Ok(Integer::I16),
+ 32 => Ok(Integer::I32),
+ 64 => Ok(Integer::I64),
+ 128 => Ok(Integer::I128),
+ _ => Err(format!("rust does not support integers with {} bits", size.bits())),
+ }
+ }
+}
+
+/// Fundamental unit of memory access and layout.
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub enum Primitive {
+ /// The `bool` is the signedness of the `Integer` type.
+ ///
+ /// One would think we would not care about such details this low down,
+ /// but some ABIs are described in terms of C types and ISAs where the
+ /// integer arithmetic is done on {sign,zero}-extended registers, e.g.
+ /// a negative integer passed by zero-extension will appear positive in
+ /// the callee, and most operations on it will produce the wrong values.
+ Int(Integer, bool),
+ F32,
+ F64,
+ Pointer,
+}
+
+impl Primitive {
+ pub fn size<C: HasDataLayout>(self, cx: &C) -> Size {
+ let dl = cx.data_layout();
+
+ match self {
+ Int(i, _) => i.size(),
+ F32 => Size::from_bits(32),
+ F64 => Size::from_bits(64),
+ Pointer => dl.pointer_size,
+ }
+ }
+
+ pub fn align<C: HasDataLayout>(self, cx: &C) -> AbiAndPrefAlign {
+ let dl = cx.data_layout();
+
+ match self {
+ Int(i, _) => i.align(dl),
+ F32 => dl.f32_align,
+ F64 => dl.f64_align,
+ Pointer => dl.pointer_align,
+ }
+ }
+
+ // FIXME(eddyb) remove, it's trivial thanks to `matches!`.
+ #[inline]
+ pub fn is_float(self) -> bool {
+ matches!(self, F32 | F64)
+ }
+
+ // FIXME(eddyb) remove, it's completely unused.
+ #[inline]
+ pub fn is_int(self) -> bool {
+ matches!(self, Int(..))
+ }
+
+ #[inline]
+ pub fn is_ptr(self) -> bool {
+ matches!(self, Pointer)
+ }
+}
+
+/// Inclusive wrap-around range of valid values, that is, if
+/// start > end, it represents `start..=MAX`,
+/// followed by `0..=end`.
+///
+/// That is, for an i8 primitive, a range of `254..=2` means following
+/// sequence:
+///
+/// 254 (-2), 255 (-1), 0, 1, 2
+///
+/// This is intended specifically to mirror LLVM’s `!range` metadata semantics.
+#[derive(Clone, Copy, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub struct WrappingRange {
+ pub start: u128,
+ pub end: u128,
+}
+
+impl WrappingRange {
+ pub fn full(size: Size) -> Self {
+ Self { start: 0, end: size.unsigned_int_max() }
+ }
+
+ /// Returns `true` if `v` is contained in the range.
+ #[inline(always)]
+ pub fn contains(&self, v: u128) -> bool {
+ if self.start <= self.end {
+ self.start <= v && v <= self.end
+ } else {
+ self.start <= v || v <= self.end
+ }
+ }
+
+ /// Returns `self` with replaced `start`
+ #[inline(always)]
+ pub fn with_start(mut self, start: u128) -> Self {
+ self.start = start;
+ self
+ }
+
+ /// Returns `self` with replaced `end`
+ #[inline(always)]
+ pub fn with_end(mut self, end: u128) -> Self {
+ self.end = end;
+ self
+ }
+
+ /// Returns `true` if `size` completely fills the range.
+ #[inline]
+ pub fn is_full_for(&self, size: Size) -> bool {
+ let max_value = size.unsigned_int_max();
+ debug_assert!(self.start <= max_value && self.end <= max_value);
+ self.start == (self.end.wrapping_add(1) & max_value)
+ }
+}
+
+impl fmt::Debug for WrappingRange {
+ fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+ if self.start > self.end {
+ write!(fmt, "(..={}) | ({}..)", self.end, self.start)?;
+ } else {
+ write!(fmt, "{}..={}", self.start, self.end)?;
+ }
+ Ok(())
+ }
+}
+
+/// Information about one scalar component of a Rust type.
+#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub enum Scalar {
+ Initialized {
+ value: Primitive,
+
+ // FIXME(eddyb) always use the shortest range, e.g., by finding
+ // the largest space between two consecutive valid values and
+ // taking everything else as the (shortest) valid range.
+ valid_range: WrappingRange,
+ },
+ Union {
+ /// Even for unions, we need to use the correct registers for the kind of
+ /// values inside the union, so we keep the `Primitive` type around. We
+ /// also use it to compute the size of the scalar.
+ /// However, unions never have niches and even allow undef,
+ /// so there is no `valid_range`.
+ value: Primitive,
+ },
+}
+
+impl Scalar {
+ #[inline]
+ pub fn is_bool(&self) -> bool {
+ matches!(
+ self,
+ Scalar::Initialized {
+ value: Int(I8, false),
+ valid_range: WrappingRange { start: 0, end: 1 }
+ }
+ )
+ }
+
+ /// Get the primitive representation of this type, ignoring the valid range and whether the
+ /// value is allowed to be undefined (due to being a union).
+ pub fn primitive(&self) -> Primitive {
+ match *self {
+ Scalar::Initialized { value, .. } | Scalar::Union { value } => value,
+ }
+ }
+
+ pub fn align(self, cx: &impl HasDataLayout) -> AbiAndPrefAlign {
+ self.primitive().align(cx)
+ }
+
+ pub fn size(self, cx: &impl HasDataLayout) -> Size {
+ self.primitive().size(cx)
+ }
+
+ #[inline]
+ pub fn to_union(&self) -> Self {
+ Self::Union { value: self.primitive() }
+ }
+
+ #[inline]
+ pub fn valid_range(&self, cx: &impl HasDataLayout) -> WrappingRange {
+ match *self {
+ Scalar::Initialized { valid_range, .. } => valid_range,
+ Scalar::Union { value } => WrappingRange::full(value.size(cx)),
+ }
+ }
+
+ #[inline]
+ /// Allows the caller to mutate the valid range. This operation will panic if attempted on a union.
+ pub fn valid_range_mut(&mut self) -> &mut WrappingRange {
+ match self {
+ Scalar::Initialized { valid_range, .. } => valid_range,
+ Scalar::Union { .. } => panic!("cannot change the valid range of a union"),
+ }
+ }
+
+ /// Returns `true` if all possible numbers are valid, i.e `valid_range` covers the whole layout
+ #[inline]
+ pub fn is_always_valid<C: HasDataLayout>(&self, cx: &C) -> bool {
+ match *self {
+ Scalar::Initialized { valid_range, .. } => valid_range.is_full_for(self.size(cx)),
+ Scalar::Union { .. } => true,
+ }
+ }
+
+ /// Returns `true` if this type can be left uninit.
+ #[inline]
+ pub fn is_uninit_valid(&self) -> bool {
+ match *self {
+ Scalar::Initialized { .. } => false,
+ Scalar::Union { .. } => true,
+ }
+ }
+}
+
+/// Describes how the fields of a type are located in memory.
+#[derive(PartialEq, Eq, Hash, Clone, Debug)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub enum FieldsShape {
+ /// Scalar primitives and `!`, which never have fields.
+ Primitive,
+
+ /// All fields start at no offset. The `usize` is the field count.
+ Union(NonZeroUsize),
+
+ /// Array/vector-like placement, with all fields of identical types.
+ Array { stride: Size, count: u64 },
+
+ /// Struct-like placement, with precomputed offsets.
+ ///
+ /// Fields are guaranteed to not overlap, but note that gaps
+ /// before, between and after all the fields are NOT always
+ /// padding, and as such their contents may not be discarded.
+ /// For example, enum variants leave a gap at the start,
+ /// where the discriminant field in the enum layout goes.
+ Arbitrary {
+ /// Offsets for the first byte of each field,
+ /// ordered to match the source definition order.
+ /// This vector does not go in increasing order.
+ // FIXME(eddyb) use small vector optimization for the common case.
+ offsets: Vec<Size>,
+
+ /// Maps source order field indices to memory order indices,
+ /// depending on how the fields were reordered (if at all).
+ /// This is a permutation, with both the source order and the
+ /// memory order using the same (0..n) index ranges.
+ ///
+ /// Note that during computation of `memory_index`, sometimes
+ /// it is easier to operate on the inverse mapping (that is,
+ /// from memory order to source order), and that is usually
+ /// named `inverse_memory_index`.
+ ///
+ // FIXME(eddyb) build a better abstraction for permutations, if possible.
+ // FIXME(camlorn) also consider small vector optimization here.
+ memory_index: Vec<u32>,
+ },
+}
+
+impl FieldsShape {
+ #[inline]
+ pub fn count(&self) -> usize {
+ match *self {
+ FieldsShape::Primitive => 0,
+ FieldsShape::Union(count) => count.get(),
+ FieldsShape::Array { count, .. } => count.try_into().unwrap(),
+ FieldsShape::Arbitrary { ref offsets, .. } => offsets.len(),
+ }
+ }
+
+ #[inline]
+ pub fn offset(&self, i: usize) -> Size {
+ match *self {
+ FieldsShape::Primitive => {
+ unreachable!("FieldsShape::offset: `Primitive`s have no fields")
+ }
+ FieldsShape::Union(count) => {
+ assert!(
+ i < count.get(),
+ "tried to access field {} of union with {} fields",
+ i,
+ count
+ );
+ Size::ZERO
+ }
+ FieldsShape::Array { stride, count } => {
+ let i = u64::try_from(i).unwrap();
+ assert!(i < count);
+ stride * i
+ }
+ FieldsShape::Arbitrary { ref offsets, .. } => offsets[i],
+ }
+ }
+
+ #[inline]
+ pub fn memory_index(&self, i: usize) -> usize {
+ match *self {
+ FieldsShape::Primitive => {
+ unreachable!("FieldsShape::memory_index: `Primitive`s have no fields")
+ }
+ FieldsShape::Union(_) | FieldsShape::Array { .. } => i,
+ FieldsShape::Arbitrary { ref memory_index, .. } => memory_index[i].try_into().unwrap(),
+ }
+ }
+
+ /// Gets source indices of the fields by increasing offsets.
+ #[inline]
+ pub fn index_by_increasing_offset<'a>(&'a self) -> impl Iterator<Item = usize> + 'a {
+ let mut inverse_small = [0u8; 64];
+ let mut inverse_big = vec![];
+ let use_small = self.count() <= inverse_small.len();
+
+ // We have to write this logic twice in order to keep the array small.
+ if let FieldsShape::Arbitrary { ref memory_index, .. } = *self {
+ if use_small {
+ for i in 0..self.count() {
+ inverse_small[memory_index[i] as usize] = i as u8;
+ }
+ } else {
+ inverse_big = vec![0; self.count()];
+ for i in 0..self.count() {
+ inverse_big[memory_index[i] as usize] = i as u32;
+ }
+ }
+ }
+
+ (0..self.count()).map(move |i| match *self {
+ FieldsShape::Primitive | FieldsShape::Union(_) | FieldsShape::Array { .. } => i,
+ FieldsShape::Arbitrary { .. } => {
+ if use_small {
+ inverse_small[i] as usize
+ } else {
+ inverse_big[i] as usize
+ }
+ }
+ })
+ }
+}
+
+/// An identifier that specifies the address space that some operation
+/// should operate on. Special address spaces have an effect on code generation,
+/// depending on the target and the address spaces it implements.
+#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
+pub struct AddressSpace(pub u32);
+
+impl AddressSpace {
+ /// The default address space, corresponding to data space.
+ pub const DATA: Self = AddressSpace(0);
+}
+
+/// Describes how values of the type are passed by target ABIs,
+/// in terms of categories of C types there are ABI rules for.
+#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+
+pub enum Abi {
+ Uninhabited,
+ Scalar(Scalar),
+ ScalarPair(Scalar, Scalar),
+ Vector {
+ element: Scalar,
+ count: u64,
+ },
+ Aggregate {
+ /// If true, the size is exact, otherwise it's only a lower bound.
+ sized: bool,
+ },
+}
+
+impl Abi {
+ /// Returns `true` if the layout corresponds to an unsized type.
+ #[inline]
+ pub fn is_unsized(&self) -> bool {
+ match *self {
+ Abi::Uninhabited | Abi::Scalar(_) | Abi::ScalarPair(..) | Abi::Vector { .. } => false,
+ Abi::Aggregate { sized } => !sized,
+ }
+ }
+
+ #[inline]
+ pub fn is_sized(&self) -> bool {
+ !self.is_unsized()
+ }
+
+ /// Returns `true` if this is a single signed integer scalar
+ #[inline]
+ pub fn is_signed(&self) -> bool {
+ match self {
+ Abi::Scalar(scal) => match scal.primitive() {
+ Primitive::Int(_, signed) => signed,
+ _ => false,
+ },
+ _ => panic!("`is_signed` on non-scalar ABI {:?}", self),
+ }
+ }
+
+ /// Returns `true` if this is an uninhabited type
+ #[inline]
+ pub fn is_uninhabited(&self) -> bool {
+ matches!(*self, Abi::Uninhabited)
+ }
+
+ /// Returns `true` is this is a scalar type
+ #[inline]
+ pub fn is_scalar(&self) -> bool {
+ matches!(*self, Abi::Scalar(_))
+ }
+}
+
+#[derive(PartialEq, Eq, Hash, Clone, Debug)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub enum Variants<V: Idx> {
+ /// Single enum variants, structs/tuples, unions, and all non-ADTs.
+ Single { index: V },
+
+ /// Enum-likes with more than one inhabited variant: each variant comes with
+ /// a *discriminant* (usually the same as the variant index but the user can
+ /// assign explicit discriminant values). That discriminant is encoded
+ /// as a *tag* on the machine. The layout of each variant is
+ /// a struct, and they all have space reserved for the tag.
+ /// For enums, the tag is the sole field of the layout.
+ Multiple {
+ tag: Scalar,
+ tag_encoding: TagEncoding<V>,
+ tag_field: usize,
+ variants: IndexVec<V, LayoutS<V>>,
+ },
+}
+
+#[derive(PartialEq, Eq, Hash, Clone, Debug)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub enum TagEncoding<V: Idx> {
+ /// The tag directly stores the discriminant, but possibly with a smaller layout
+ /// (so converting the tag to the discriminant can require sign extension).
+ Direct,
+
+ /// Niche (values invalid for a type) encoding the discriminant:
+ /// Discriminant and variant index coincide.
+ /// The variant `untagged_variant` contains a niche at an arbitrary
+ /// offset (field `tag_field` of the enum), which for a variant with
+ /// discriminant `d` is set to
+ /// `(d - niche_variants.start).wrapping_add(niche_start)`.
+ ///
+ /// For example, `Option<(usize, &T)>` is represented such that
+ /// `None` has a null pointer for the second tuple field, and
+ /// `Some` is the identity function (with a non-null reference).
+ Niche { untagged_variant: V, niche_variants: RangeInclusive<V>, niche_start: u128 },
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub struct Niche {
+ pub offset: Size,
+ pub value: Primitive,
+ pub valid_range: WrappingRange,
+}
+
+impl Niche {
+ pub fn from_scalar<C: HasDataLayout>(cx: &C, offset: Size, scalar: Scalar) -> Option<Self> {
+ let Scalar::Initialized { value, valid_range } = scalar else { return None };
+ let niche = Niche { offset, value, valid_range };
+ if niche.available(cx) > 0 { Some(niche) } else { None }
+ }
+
+ pub fn available<C: HasDataLayout>(&self, cx: &C) -> u128 {
+ let Self { value, valid_range: v, .. } = *self;
+ let size = value.size(cx);
+ assert!(size.bits() <= 128);
+ let max_value = size.unsigned_int_max();
+
+ // Find out how many values are outside the valid range.
+ let niche = v.end.wrapping_add(1)..v.start;
+ niche.end.wrapping_sub(niche.start) & max_value
+ }
+
+ pub fn reserve<C: HasDataLayout>(&self, cx: &C, count: u128) -> Option<(u128, Scalar)> {
+ assert!(count > 0);
+
+ let Self { value, valid_range: v, .. } = *self;
+ let size = value.size(cx);
+ assert!(size.bits() <= 128);
+ let max_value = size.unsigned_int_max();
+
+ let niche = v.end.wrapping_add(1)..v.start;
+ let available = niche.end.wrapping_sub(niche.start) & max_value;
+ if count > available {
+ return None;
+ }
+
+ // Extend the range of valid values being reserved by moving either `v.start` or `v.end` bound.
+ // Given an eventual `Option<T>`, we try to maximize the chance for `None` to occupy the niche of zero.
+ // This is accomplished by preferring enums with 2 variants(`count==1`) and always taking the shortest path to niche zero.
+ // Having `None` in niche zero can enable some special optimizations.
+ //
+ // Bound selection criteria:
+ // 1. Select closest to zero given wrapping semantics.
+ // 2. Avoid moving past zero if possible.
+ //
+ // In practice this means that enums with `count > 1` are unlikely to claim niche zero, since they have to fit perfectly.
+ // If niche zero is already reserved, the selection of bounds are of little interest.
+ let move_start = |v: WrappingRange| {
+ let start = v.start.wrapping_sub(count) & max_value;
+ Some((start, Scalar::Initialized { value, valid_range: v.with_start(start) }))
+ };
+ let move_end = |v: WrappingRange| {
+ let start = v.end.wrapping_add(1) & max_value;
+ let end = v.end.wrapping_add(count) & max_value;
+ Some((start, Scalar::Initialized { value, valid_range: v.with_end(end) }))
+ };
+ let distance_end_zero = max_value - v.end;
+ if v.start > v.end {
+ // zero is unavailable because wrapping occurs
+ move_end(v)
+ } else if v.start <= distance_end_zero {
+ if count <= v.start {
+ move_start(v)
+ } else {
+ // moved past zero, use other bound
+ move_end(v)
+ }
+ } else {
+ let end = v.end.wrapping_add(count) & max_value;
+ let overshot_zero = (1..=v.end).contains(&end);
+ if overshot_zero {
+ // moved past zero, use other bound
+ move_start(v)
+ } else {
+ move_end(v)
+ }
+ }
+ }
+}
+
+#[derive(PartialEq, Eq, Hash, Clone)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub struct LayoutS<V: Idx> {
+ /// Says where the fields are located within the layout.
+ pub fields: FieldsShape,
+
+ /// Encodes information about multi-variant layouts.
+ /// Even with `Multiple` variants, a layout still has its own fields! Those are then
+ /// shared between all variants. One of them will be the discriminant,
+ /// but e.g. generators can have more.
+ ///
+ /// To access all fields of this layout, both `fields` and the fields of the active variant
+ /// must be taken into account.
+ pub variants: Variants<V>,
+
+ /// The `abi` defines how this data is passed between functions, and it defines
+ /// value restrictions via `valid_range`.
+ ///
+ /// Note that this is entirely orthogonal to the recursive structure defined by
+ /// `variants` and `fields`; for example, `ManuallyDrop<Result<isize, isize>>` has
+ /// `Abi::ScalarPair`! So, even with non-`Aggregate` `abi`, `fields` and `variants`
+ /// have to be taken into account to find all fields of this layout.
+ pub abi: Abi,
+
+ /// The leaf scalar with the largest number of invalid values
+ /// (i.e. outside of its `valid_range`), if it exists.
+ pub largest_niche: Option<Niche>,
+
+ pub align: AbiAndPrefAlign,
+ pub size: Size,
+}
+
+impl<V: Idx> LayoutS<V> {
+ pub fn scalar<C: HasDataLayout>(cx: &C, scalar: Scalar) -> Self {
+ let largest_niche = Niche::from_scalar(cx, Size::ZERO, scalar);
+ let size = scalar.size(cx);
+ let align = scalar.align(cx);
+ LayoutS {
+ variants: Variants::Single { index: V::new(0) },
+ fields: FieldsShape::Primitive,
+ abi: Abi::Scalar(scalar),
+ largest_niche,
+ size,
+ align,
+ }
+ }
+}
+
+impl<V: Idx> fmt::Debug for LayoutS<V> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ // This is how `Layout` used to print before it become
+ // `Interned<LayoutS>`. We print it like this to avoid having to update
+ // expected output in a lot of tests.
+ let LayoutS { size, align, abi, fields, largest_niche, variants } = self;
+ f.debug_struct("Layout")
+ .field("size", size)
+ .field("align", align)
+ .field("abi", abi)
+ .field("fields", fields)
+ .field("largest_niche", largest_niche)
+ .field("variants", variants)
+ .finish()
+ }
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+pub enum PointerKind {
+ /// Most general case, we know no restrictions to tell LLVM.
+ SharedMutable,
+
+ /// `&T` where `T` contains no `UnsafeCell`, is `dereferenceable`, `noalias` and `readonly`.
+ Frozen,
+
+ /// `&mut T` which is `dereferenceable` and `noalias` but not `readonly`.
+ UniqueBorrowed,
+
+ /// `&mut !Unpin`, which is `dereferenceable` but neither `noalias` nor `readonly`.
+ UniqueBorrowedPinned,
+
+ /// `Box<T>`, which is `noalias` (even on return types, unlike the above) but neither `readonly`
+ /// nor `dereferenceable`.
+ UniqueOwned,
+}
+
+#[derive(Copy, Clone, Debug)]
+pub struct PointeeInfo {
+ pub size: Size,
+ pub align: Align,
+ pub safe: Option<PointerKind>,
+ pub address_space: AddressSpace,
+}
+
+/// Used in `might_permit_raw_init` to indicate the kind of initialisation
+/// that is checked to be valid
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum InitKind {
+ Zero,
+ UninitMitigated0x01Fill,
+}
+
+impl<V: Idx> LayoutS<V> {
+ /// Returns `true` if the layout corresponds to an unsized type.
+ pub fn is_unsized(&self) -> bool {
+ self.abi.is_unsized()
+ }
+
+ pub fn is_sized(&self) -> bool {
+ self.abi.is_sized()
+ }
+
+ /// Returns `true` if the type is a ZST and not unsized.
+ pub fn is_zst(&self) -> bool {
+ match self.abi {
+ Abi::Scalar(_) | Abi::ScalarPair(..) | Abi::Vector { .. } => false,
+ Abi::Uninhabited => self.size.bytes() == 0,
+ Abi::Aggregate { sized } => sized && self.size.bytes() == 0,
+ }
+ }
+}
+
+#[derive(Copy, Clone, Debug)]
+pub enum StructKind {
+ /// A tuple, closure, or univariant which cannot be coerced to unsized.
+ AlwaysSized,
+ /// A univariant, the last field of which may be coerced to unsized.
+ MaybeUnsized,
+ /// A univariant, but with a prefix of an arbitrary size & alignment (e.g., enum tag).
+ Prefixed(Size, Align),
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-17 10:14:17 +0000